Increasing integration of optical components on photonic integrated circuits (PICs) provides the ability to provide increasingly sophisticated optical devices using a single substrate. Usually such devices include optical path length adjusters, e.g. thermo-optical phase shifter, to adjust the optical path length of one or more optical waveguides on the PIC. Such path length adjusters add complexity and cost to optical systems, typically including power sources to power the path length adjuster, and a feedback control system to maintain a desired phase shift in the adjusted path.